Anal Fissure Location and Characteristics

Anatomical Distribution

• Approximately 90% of anal fissures occur posteriorly in the midline of the anal canal, with the remainder occurring anteriorly, representing a significant majority of all anal fissures 1, 2
• Posterior midline fissures are the most common location, representing the majority of all anal fissures 3, 4
• Anterior midline fissures occur less frequently, seen in approximately 10% of women versus only 1% of men 1, 2

Atypical Fissure Locations and Associated Conditions

• Atypical fissure locations, such as lateral or multiple fissures, should raise suspicion for underlying conditions like inflammatory bowel disease (IBD), sexually transmitted diseases (HIV, syphilis, herpes), anorectal cancer, tuberculosis, leukemia, or other infectious causes 1, 2, 3, 4

Anatomical Description

• Anal fissures are longitudinal tears in the squamous epithelium at or just inside the anal verge, which can extend from the dentate line to the anal verge 1, 2, 3, 4
• Chronic fissures may display signs of chronicity, including a sentinel skin tag, hypertrophied anal papilla, fibrosis, or visible internal sphincter muscle at the fissure base 3, 4

Pathophysiology

• Internal anal sphincter hypertonia correlates with decreased anodermal vascular blood flow, contributing to the development of anal fissures 1, 2
• Contrary to common belief, less than 25% of patients with anal fissures complain of constipation, highlighting the complexity of the condition 1, 2

Clinical Relevance

• Understanding the typical location of anal fissures helps in diagnosis and treatment planning, as atypical locations may prompt investigation for underlying conditions 1, 2, 3, 4

Diagnostic Approach

• Fissures are best visualized by effacing the anal canal with opposing traction on the buttocks, and additional investigations like endoscopy, CT scan, MRI, or endoanal ultrasound may be necessary for atypical fissures 1, 2, 3, 4

Pelvic Floor Dysfunction and Anal Fissures

Introduction to Pelvic Floor Dysfunction

• The American College of Surgeons suggests that pelvic floor dysfunction does not cause typical anal fissures, but it is a significant contributing factor that perpetuates and prevents healing of chronic fissures through increased internal anal sphincter tone and dyssynergia 5
• The World Journal of Emergency Surgery reports that the exact etiology of typical anal fissures remains incompletely understood, but the evidence points to a multifactorial process rather than a single causative mechanism 5

Clinical Evidence for Pelvic Floor Dysfunction

• The World Journal of Emergency Surgery states that mechanical trauma alone is insufficient to explain anal fissure development, as less than 25% of patients with anal fissures actually complain of constipation or report passage of hard stools 5
• The World Journal of Emergency Surgery indicates that internal anal sphincter hypertonia is strongly correlated with decreased anodermal vascular blood flow, supporting the ischemic ulcer theory as a primary pathophysiologic mechanism 5
• Typical anal fissures are defined by their location (90% posterior midline, with anterior fissures in 10% of women versus 1% of men) and should not be confused with atypical fissures that suggest underlying pathology 5

Treatment Approach for Typical Fissures

• The World Journal of Emergency Surgery recommends that acute fissures should receive conservative management including dietary fiber, increased water intake, and sitz baths as first-line treatment 6
• The World Journal of Emergency Surgery suggests that patients with typical anal fissures should not be assumed to have constipation as the primary problem—the majority do not report this symptom 5

Hilton's Line in Anal Fissure Diagnosis and Treatment

Anatomical Significance and Diagnostic Importance

• The presence of associated findings near Hilton's line, including a sentinel skin tag just distal to the fissure and a hypertrophied anal papilla at its proximal margin, indicates chronicity, as noted by the American Gastroenterological Association 7

Clinical Examination Technique

• In the setting of marked pain or tenderness, instrumentation of the anal canal is inappropriate and traumatic; examination under anesthesia is warranted when significant anal pain cannot be diagnosed comfortably, according to the American Gastroenterological Association 7
• Fissures cannot be visualized with end-viewing endoscopes—direct visualization with buttock traction is required, as recommended by the American Gastroenterological Association 7

Secondary Etiologies of Atypical Anal Fissures

Inflammatory Bowel Disease

• In patients with Crohn’s disease, atypical (off‑midline) anal fissures are frequently associated with perianal fistulae, which occur in 13 %–27 % of this population【8】.
• Among individuals who develop perianal disease, up to 81 % present initially with a perianal fistula, indicating that fistulae can be the first manifestation of Crohn’s disease【8】.

Infectious Causes

• Recognized infectious agents that can produce atypical anal fissures include syphilis, herpes simplex virus, Mycobacterium tuberculosis, and actinomycosis【8】.

Radiation‑Related Etiology

• Radiation proctitis occurring after pelvic radiation therapy is an established cause of atypical anal fissures【8】.

Traumatic Etiology

• Foreign‑body trauma to the anorectal region can precipitate the development of atypical fissures【8】.

Prior Surgical History

• A history of prior anal surgery is a documented risk factor for the emergence of atypical (lateral or multiple) anal fissures【8】.